Organic-inorganic polymer hybrids, wherein inorganic solids on a nano or molecular level are dispersed in organic polymers, have raised a great deal of scientific, technological and industrial interests because of their unique properties.
To elaborate organic-inorganic polymer hybrid composites, a sol-gel process using metal alkoxides is the most useful and important approach. By properly controlling the reaction conditions of hydrolysis and polycondensation of metal alkoxydes, in particular of alkoxysilanes (e.g. tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS)), in the presence of pre-formed organic polymers, it is possible to obtain hybrids with improved properties compared to the original compounds. The polymer can enhance the toughness and processability of otherwise brittle inorganic materials, wherein the inorganic network can enhance scratch resistance, mechanical properties and surface characteristics of said hybrids.
Hybrids made from sol-gel technique starting from fluoropolymers, in particular from vinylidene fluoride polymers are known in the art.
For instance, WO 2011/121078 (SOLVAY SOLEXIS S.P.A.) Jun. 10, 2011 discloses a process for the manufacture of fluoropolymer hybrid organic-inorganic composites wherein at least a fraction of hydroxyl groups of a fluoropolymer are reacted in solution or in molten state with at least a fraction of hydrolysable groups of a metal compound of formula X4-mAYm (X is a hydrocarbon group, Y is a hydrolysable group, A is a metal selected from Si, Ti and Zr, m is an integer from 1 to 4). The hydrolysis and/or polycondensation of said metal compound or of pendant —Ym-1AX4-m groups can be carried out simultaneously to the step of reacting the hydroxyl groups of the fluoropolymer and the metal compound or can be carried out once said reaction has occurred. In case of reaction between said fluoropolymer and said metal compound in the molten state, the hydrolysis and/or polycondensation is preferably promoted by injection of water vapour, optionally in combination with a volatile acid catalyst.